Hard disk drives are used in almost all computer system operations. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model includes a storage disk or hard disk that spins at a designed rotational speed. An actuator arm is utilized to reach out over the disk. The arm carries a head assembly that has a magnetic read/write transducer or head for reading/writing information to or from a location on the disk. The transducer is attached to a slider, such as an air-bearing slider, which is supported adjacent to the data surface of the disk by a cushion of air generated by the rotating disk. The transducer can also be attached to a contact-recording type slider. In either case, the slider is connected to the actuator arm by means of a suspension. The complete head assembly, e.g., the suspension and head, is called a head gimbal assembly (HGA).
In operation, the hard disk is rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are tracks evenly spaced at known intervals across the disk. When a request for a read of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk aligns the head, via the arm, over the specific track location and the head writes the information to the disk.
Over the years, the disk and the head have undergone great reductions in their size. Much of the refinement has been driven by consumer demand for smaller and more portable hard drives such as those used in personal digital assistants (PDAs), MP3 players, and the like. For example, the original hard disk drive had a disk diameter of 24 inches. Modern hard disk drives are much smaller and include disk diameters of less than 2.5 inches (micro drives are significantly smaller than that). Advances in magnetic recording are also primary reasons for the reduction in size.
Another advancement to the hard disk drive is the use of smaller components. For example, by reducing the read/write tolerances of the head portion, the tracks on the disk can be reduced in size by the same margin. Thus, as modern micro recognition technology is applied to the head, the track size on the disk can be further compressed thereby enabling more tracks to be included on the disk, resulting in the disk having an increase data storage capacity.
Yet another advancement to the hard disk drive is the reduction of the “flying” height at which the magnetic read/write transducer head operates or flies above the disk. As the flying height has been continually reduced, a greater number of data can be stored on a disk surface. Given this advantage, some have reduced the flying height of the head to zero in order to implement contact recording to further increase the amount of data that can be stored by the disk. Ideally, in contact recording the magnetic read/write transducer head is in contact with the disk. However, there are disadvantages associated with this technique.
For example, contact recording or partial contact recording schemes suffer from high friction and wear of the read/write transducer head, which can be caused by the slider bouncing. Note that the amount of slide bounce is a function of the slider trailing pad area, roughness of the disk, and the properties of the lubricant on the disk. Note that it has been shown that higher disk roughness and smaller trailing pad area are able to reduce friction and bounce. However, that technique usually leads to large wear rates. Another technique to reduce slider friction wear and bounce has been to reduce the surface energy of the slider by coating it with polytetrafluoroethylene (PTFE) films, anti-wearing agents, or fluorinated carbon. The drawback of adding these films onto the slider is that they raise the slider fly height or magnetic spacing and that they wear off easily.